Changes Of Antioxidative Responses And Proline Metabolism In Nitraria Tangutorum Bobr. Callus Under Exogenous Nitric Oxide Treatment

Nitric oxide （NO） is a kind of bioactive gases molecules, widely distributed in theorganisms, NO can be produced through enzymes and non-enzymatic pathway in theplant．By reason that NO is a kind of amphoteric molecules with highly reactive, hasdouble effects of poison and protect cells in plants, the effect is relative to NO effectiveconcentration and intracellular physiological environment．As a signaling molecule, NOis involved in seed germination and plant growth, morphogenesis, regulation of stomatalmovement, respiration, aging and programmed cell death, and makes response to thebiological and abiotic stress．Sodium nitroprusside （SNP） is a kind of exogenous NOdonor, after plant cell absorbed SNP, it will be degraded and release NO, SNP iscommonly used in research the effect of NO．Nitraria tangutorum Bobr. is mainlydistributed in arid desert region, can adapt to harsh habitat．It is one of importantdominant species in saline-alkali desert, not only possesses excellent ecological function,but also has high economic and medicinal value．In this paper, Nitraria tangutorumBobr. callus was employed to study the relationship between exogenous NO treatmentand changes of oxidative responses and proline metabolism, aimed to revealing themechanism of NO is involved in regulation of plant resistance,.The main results were asfollows：1．Under25and100μmol· L^-1SNP treatment, weakened malondialdehyde（MDA）content in Nitraria tangutorum Bobr. callus, while no changes was observed aftertrentment with25μmol· L^-1SNP for1d．Compared to the control, SNP treatmentinduced remarkable increase in superoxide dismutase（SOD） activity, but nosignificant changes between different SNP concentration； The activity ofcatalase（CAT） and glutathione reductase（GR） are inhibited significantly, whilebrought increase in the ascorbate peroxidase（APX） activity； Treaterment with25μmol· L^-1SNP, the activity of peroxidase（POD） increased, respectively, thendecreasing after treatment with100μmol· L^-1SNP for3d．2． Compared to the control, there was remarlable increase of superoxide anion（O2–）content after treatment with different SNP concentration, however, the amountof hydroxyl radicals（·OH） decreased in Nitraria tangutorum Bobr. callus；After treatment with25μmol· L^-1SNP, brought decrease in the amount of hydrogenperoxide （H₂O₂）, the content of H₂O₂was firstly decreasing treatment with100μmol· L^-1SNP, then increasing with prolonging time of treatment, respectively．3．A significant increased in solubie protein content and decreased in proline content wasobserved in Nitraria tangutorum Bobr．callus exposed to25and100μmol· L^-1SNP；Analysis of enzyme activites showed that exogenous NO induced increase inornithine aminotransferase（OAT） activity and proline dehydrogenase（ProDH） activity and decrease in glutamylkinasa（GK） activity, respectively．In conclusion, these results suggested that:①Exogenous NO led to significantelevation in the activity of SOD、POD and APX, cleared H₂O₂and·OH, relieving thedamage of membrane lipid peroxidation by the accumlation of ROS．②Exogenous NOmight participate in the anabolism of protein in Nitraria tangutorum Bobr．callus., butdecreasing the content of proline was observed, which was associated with the decreaseof GK activity and increase of ProDH activity induced by different SNP concentraction．...